fix!: update multi-select-combo-box to synchronize on change

vaadin-combo-box-flow-parent/vaadin-combo-box-flow-integration-tests/src/main/java/com/vaadin/flow/component/combobox/test/MultiSelectComboBoxPushValueChangePage.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2000-2026 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.component.combobox.test;
+
+import java.util.List;
+import java.util.Set;
+
+import com.vaadin.flow.component.UI;
+import com.vaadin.flow.component.combobox.MultiSelectComboBox;
+import com.vaadin.flow.component.html.Div;
+import com.vaadin.flow.component.html.NativeButton;
+import com.vaadin.flow.router.Route;
+import com.vaadin.flow.shared.communication.PushMode;
+
+/**
+ * Reproduces the scenario from
+ * <a href="https://github.com/vaadin/flow-components/issues/9611">#9611</a>:
+ * with push enabled, two separate push frames around a server-side
+ * {@code setValue} must not relay a spurious client-initiated value change with
+ * an empty value back to the server.
+ */
+@Route("vaadin-multi-select-combo-box/push-value-change")
+public class MultiSelectComboBoxPushValueChangePage extends Div {
+    public MultiSelectComboBoxPushValueChangePage() {
+        UI.getCurrent().getPushConfiguration().setPushMode(PushMode.AUTOMATIC);
+
+        Div log = new Div();
+        log.setId("value-change-log");
+
+        NativeButton runScenario = new NativeButton("Run #9611 scenario",
+                event -> {
+                    MultiSelectComboBox<String> comboBox = new MultiSelectComboBox<>();
+                    comboBox.setItems(List.of("1", "2", "3"));
+
+                    comboBox.addValueChangeListener(e -> {
+                        Div entry = new Div();
+                        entry.setText("isFromClient=%s old=%s new=%s value=%s"
+                                .formatted(e.isFromClient(), e.getOldValue(),
+                                        e.getValue(), comboBox.getValue()));
+                        log.add(entry);
+                    });
+
+                    add(comboBox);
+
+                    UI ui = UI.getCurrent();
+                    ui.push();
+                    comboBox.setValue(Set.of("1"));
+                    ui.push();
+                });
+        runScenario.setId("run-scenario");
+
+        add(runScenario, log);
+    }
+}

vaadin-combo-box-flow-parent/vaadin-combo-box-flow-integration-tests/src/main/java/com/vaadin/flow/component/combobox/test/MultiSelectComboBoxUserValueChangePage.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2000-2026 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.component.combobox.test;
+
+import java.util.List;
+
+import com.vaadin.flow.component.combobox.MultiSelectComboBox;
+import com.vaadin.flow.component.html.Div;
+import com.vaadin.flow.component.html.Span;
+import com.vaadin.flow.router.Route;
+
+/**
+ * View used to verify that genuine user value commits (dropdown selection and
+ * deselection, clear-button click, chip removal, Esc-clear) still propagate the
+ * value to the server after the value sync was switched from the
+ * {@code selected-items-changed} property notification to the {@code change}
+ * event (see
+ * <a href="https://github.com/vaadin/flow-components/issues/9611">#9611</a>).
+ */
+@Route("vaadin-multi-select-combo-box/user-value-change")
+public class MultiSelectComboBoxUserValueChangePage extends Div {
+    public MultiSelectComboBoxUserValueChangePage() {
+        MultiSelectComboBox<String> comboBox = new MultiSelectComboBox<>(
+                "Items");
+        comboBox.setItems(List.of("Item 1", "Item 2", "Item 3"));
+        comboBox.setWidth("500px");
+        // Clear button must be visible for the clear-button and Esc-to-clear
+        // user paths to clear the selection.
+        comboBox.setClearButtonVisible(true);
+
+        Span eventValue = new Span();
+        eventValue.setId("event-value");
+        Span eventOrigin = new Span();
+        eventOrigin.setId("event-origin");
+        Span eventCount = new Span("0");
+        eventCount.setId("event-count");
+
+        comboBox.addValueChangeListener(e -> {
+            eventValue.setText(String.join(",", e.getValue()));
+            eventOrigin.setText(e.isFromClient() ? "client" : "server");
+            eventCount.setText(
+                    String.valueOf(Integer.parseInt(eventCount.getText()) + 1));
+        });
+
+        add(comboBox);
+        add(new Div(new Span("Event value: "), eventValue));
+        add(new Div(new Span("Event origin: "), eventOrigin));
+        add(new Div(new Span("Event count: "), eventCount));
+    }
+}

vaadin-combo-box-flow-parent/vaadin-combo-box-flow-integration-tests/src/test/java/com/vaadin/flow/component/combobox/test/MultiSelectComboBoxPushValueChangeIT.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2000-2026 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.component.combobox.test;
+
+import java.util.List;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.vaadin.flow.testutil.TestPath;
+import com.vaadin.testbench.TestBenchElement;
+import com.vaadin.tests.AbstractComponentIT;
+
+/**
+ * Regression test for
+ * <a href="https://github.com/vaadin/flow-components/issues/9611">#9611</a>:
+ * with {@code @Push} enabled, a server-side {@code setValue} surrounded by two
+ * push frames must not produce a spurious client-initiated value change with an
+ * empty value.
+ */
+@TestPath("vaadin-multi-select-combo-box/push-value-change")
+public class MultiSelectComboBoxPushValueChangeIT extends AbstractComponentIT {
+    private TestBenchElement runScenario;
+    private TestBenchElement log;
+
+    @Before
+    public void init() {
+        open();
+        runScenario = $("button").waitForFirst();
+        log = $("div").id("value-change-log");
+    }
+
+    @Test
+    public void setValueWithPushFrames_noSpuriousEmptyClientValueChange() {
+        runScenario.click();
+
+        // Wait for the value change triggered by the server-side setValue
+        waitUntil(driver -> !log.getText().isEmpty());
+
+        List<String> entries = getLogEntries();
+
+        // No client-initiated value change with an empty value must occur
+        for (String entry : entries) {
+            boolean isFromClient = entry.contains("isFromClient=true");
+            boolean isEmptyValue = entry.contains("value=[]");
+            Assert.assertFalse(
+                    "Spurious client-initiated value change with empty value: "
+                            + entry,
+                    isFromClient && isEmptyValue);
+        }
+
+        // The final server value must remain ["1"]
+        String last = entries.get(entries.size() - 1);
+        Assert.assertTrue(
+                "Expected final value to remain [1], but log was: " + entries,
+                last.contains("value=[1]"));
+    }
+
+    private List<String> getLogEntries() {
+        return log.$("div").all().stream().map(TestBenchElement::getText)
+                .toList();
+    }
+}

vaadin-combo-box-flow-parent/vaadin-combo-box-flow-integration-tests/src/test/java/com/vaadin/flow/component/combobox/test/MultiSelectComboBoxUserValueChangeIT.java

@@ -0,0 +1,114 @@
+/*
+ * Copyright 2000-2026 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.component.combobox.test;
+
+import java.util.List;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.openqa.selenium.Keys;
+
+import com.vaadin.flow.component.combobox.testbench.MultiSelectComboBoxElement;
+import com.vaadin.flow.testutil.TestPath;
+import com.vaadin.testbench.TestBenchElement;
+import com.vaadin.tests.AbstractComponentIT;
+
+/**
+ * Verifies that genuine user value commits still propagate to the server after
+ * the value sync was switched from the {@code selected-items-changed} property
+ * notification to the {@code change} event (see
+ * <a href="https://github.com/vaadin/flow-components/issues/9611">#9611</a>).
+ */
+@TestPath("vaadin-multi-select-combo-box/user-value-change")
+public class MultiSelectComboBoxUserValueChangeIT extends AbstractComponentIT {
+    private MultiSelectComboBoxElement comboBox;
+    private TestBenchElement eventValue;
+    private TestBenchElement eventOrigin;
+
+    @Before
+    public void init() {
+        open();
+        comboBox = $(MultiSelectComboBoxElement.class).waitForFirst();
+        eventValue = $("span").id("event-value");
+        eventOrigin = $("span").id("event-origin");
+    }
+
+    @Test
+    public void selectItem_valuePropagatedToServer() {
+        clickItem("Item 1");
+
+        waitUntil(driver -> "Item 1".equals(eventValue.getText()));
+        Assert.assertEquals("client", eventOrigin.getText());
+    }
+
+    @Test
+    public void deselectItem_valuePropagatedToServer() {
+        clickItem("Item 1");
+        waitUntil(driver -> "Item 1".equals(eventValue.getText()));
+
+        clickItem("Item 1");
+        waitUntil(driver -> eventValue.getText().isEmpty());
+        Assert.assertEquals("client", eventOrigin.getText());
+    }
+
+    @Test
+    public void clickClearButton_valuePropagatedToServer() {
+        clickItem("Item 1");
+        waitUntil(driver -> "Item 1".equals(eventValue.getText()));
+
+        comboBox.$("[part~='clear-button']").first().click();
+
+        waitUntil(driver -> eventValue.getText().isEmpty());
+        Assert.assertEquals("client", eventOrigin.getText());
+    }
+
+    @Test
+    public void removeChip_valuePropagatedToServer() {
+        clickItem("Item 1");
+        waitUntil(driver -> "Item 1".equals(eventValue.getText()));
+
+        comboBox.$("vaadin-multi-select-combo-box-chip").get(1)
+                .$("[part~='remove-button']").first().click();
+
+        waitUntil(driver -> eventValue.getText().isEmpty());
+        Assert.assertEquals("client", eventOrigin.getText());
+    }
+
+    @Test
+    public void pressEscapeToClear_valuePropagatedToServer() {
+        clickItem("Item 1");
+        waitUntil(driver -> "Item 1".equals(eventValue.getText()));
+
+        comboBox.sendKeys(Keys.ESCAPE);
+
+        waitUntil(driver -> eventValue.getText().isEmpty());
+        Assert.assertEquals("client", eventOrigin.getText());
+    }
+
+    private void clickItem(String label) {
+        comboBox.openPopup();
+        comboBox.waitForLoadingFinished();
+        List<TestBenchElement> items = comboBox
+                .$("vaadin-multi-select-combo-box-item").all();
+        TestBenchElement item = items.stream()
+                .filter(el -> label.equals(el.getText())).findFirst()
+                .orElseThrow(() -> new AssertionError(
+                        "Item not found in dropdown: " + label));
+        item.click();
+        comboBox.closePopup();
+    }
+}

vaadin-combo-box-flow-parent/vaadin-combo-box-flow/src/main/java/com/vaadin/flow/component/combobox/MultiSelectComboBox.java

@@ -135,6 +135,8 @@ public MultiSelectComboBox(int pageSize) {
                 MultiSelectComboBox::presentationToModel,
                 MultiSelectComboBox::modelToPresentation);
 
+        setSynchronizedEvent("change");
+
         // Create the selection model that manages the currently selected items.
         // The model ensures that items are compared based on their data
         // provider identify, and that the selection only changes if items

vaadin-combo-box-flow-parent/vaadin-combo-box-testbench/src/main/java/com/vaadin/flow/component/combobox/testbench/MultiSelectComboBoxElement.java

@@ -102,6 +102,7 @@ public void selectByText(String label) {
                 "const isSelected = combobox.selectedItems.some(item => item.key === itemToSelect.key);" +
                 "if (!isSelected) {" +
                 "  combobox.selectedItems = [...combobox.selectedItems, itemToSelect];" +
+                "  combobox.dispatchEvent(new CustomEvent('change', { bubbles: true }));" +
                 "}" +
                 "return true;";
         //@formatter:on
@@ -128,6 +129,7 @@ public void deselectByText(String label) {
                 "const isSelected = combobox.selectedItems.some(item => item.label === label);" +
                 "if (isSelected) {" +
                 "  combobox.selectedItems = combobox.selectedItems.filter(item => item.label !== label);" +
+                "  combobox.dispatchEvent(new CustomEvent('change', { bubbles: true }));" +
                 "}";
         //@formatter:on
         executeScript(script, this, label);
@@ -137,7 +139,13 @@ public void deselectByText(String label) {
      * Deselects all items, effectively clearing the value.
      */
     public void deselectAll() {
-        String script = "const combobox = arguments[0]; combobox.selectedItems = [];";
+        //@formatter:off
+        String script =
+                "const combobox = arguments[0];" +
+                "if (combobox.selectedItems.length) {" +
+                "  combobox.clear();" +
+                "}";
+        //@formatter:on
         executeScript(script, this);
     }